Circuit breakers are one of a variety of overcurrent protection devices used for circuit protection and isolation. The circuit breaker provides electrical protection whenever an electric abnormality occurs. In a typical circuit breaker, current enters the system from a power line and passes through a line conductor to a stationary contact fixed on the line conductor, then to a movable contact. The movable contact is fixedly attached to a pivoting arm. As long as the stationary and movable contacts are in physical contact, current passes from the stationary contact to the movable contact and out of the circuit breaker to down-line electrical devices.
In the event of an overcurrent condition (short circuit or extended conducting time greater than device rated current), the device responds by “tripping”. The armature will disengage the cradle allowing it to rotate to a second position. This position reorients the breaker mechanism and stored energy of the mechanism spring to (1) compel the device operating handle to move to a secondary position and (2) separate the contacts in order to stop the flow of electrical current.
As is well known to those of skill in the art, common trip cams provide a mechanical link between poles of a breaker to ensure all poles trip when one of them trips. Traditionally, common trip cams that are used in high rated miniature circuits breakers (70 A and above) are made of relatively expensive materials that prevent the cam from melting when in contact with the armature. The material is also flexible to account for pole to pole tolerance variations and calibration differences that may otherwise defeat the common trip function. FIG. 1 is an example of a prior art common trip cam.